Seepage Studies Using Tracers and the Self Potential Test

by Grady W. Williams, US Army Corps of Engineers, Walla, Walla, WA, USA,

Document Type: Proceeding Paper

Part of: Use of In Situ Tests in Geotechnical Engineering


Mill Creek Dam, a homogeneous silt structure resting on a conglomerate foundation, has experienced severe 'seepage since its construction in 1941. In 1981, a concrete cutoff wall was constructed to reduce seepage and piping potential. Two-well tracer tests were performed to measure seepage existence, velocity, and direction. Only one of three such tests resulted in detection of the tracer. This test yielded a seepage velocity of 5. 5 feet/minute, but a back-computation of porosity rendered the results questionable. A point-dilution tracer test was performed to measure seepage existence, filtration velocity, and permeability. The test proved successful, yielding a filtration velocity of 8. 9 multiplied by 10** minus 5 feet/minute and a permeability of 3. 0 multiplied by 10** minus 3 feet/minute. The self potential test was successfully used to locate anomalous zones of seepage along the length of the cutoff wall.

Subject Headings: Seepage | Probe instruments | Soil tests | Diaphragm walls | Fluid velocity | Dam foundations | Filtration | Embankment dams

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